I. Field of the Invention
The present invention relates generally to the field of container lids, and more particularly, to a lid for use in an environment wherein a vessel is to be covered to minimize evaporation of the fluid therefrom and yet a lid that has openings therein, which openings are capable of being utilized to gain admittance to the interior of the vessel without the lid being removed therefrom.
II. Description of the Prior Art
In the field of pharmaceutical testing, the instruments and mechanisms which are utilized to test certain pharmaceutical compounds require extreme accuracy and repeatability of the tests. Such testing equipment is well known in the prior art and is widely available and utilized. In certain test procedures, specifically in dissolution tests wherein timed release capsules and tablets are tested, it is necessary to measure the dissolution of such tablets and capsules over an extended period time while maintaining the level of solution and the temperature thereof within precise limits.
The vessels which typically are utilized have test instruments placed therein and means to maintain a constant environment for the testing solution. However, there is quite a problem in maintaining the level of solution over an extended period of time, and yet being able to monitor the solution and to take samples therefrom at convenient times. Typically if the solution container is open to the ambient atmosphere then there is considerable evaporation from the solution thereby giving incorrect results from the test. In addition, open containers make it harder to maintain a consistent temperature level of the solution.
In the past, certain inert lids have been utilized to cover the containers, but the lids must be preformed with slots and holes therein by which testing instruments and sampling devices may be placed to effect the monitoring of the solution. Obviously, with a fixed lid having fixed apertures therein, it is difficult to effect testing procedures by inserting and removing stirrers, pipettes, thermometers and other monitoring devices without removing the lid entirely or without compromising the results of the solution by evaporative loss or lack of temperature control. The prior art devices have proven to be less than satisfactory in actual use.